Jet pump having unevenly spaced blades

ABSTRACT

The invention is directed to a thick stator vane that effects continuous acceleration of the water stream within the jet pump, a non-uniform spacing of stator vanes or impeller blades to reduce noise output of the jet pump during operation, and a coupling structure positioned between the impeller and engine that prevents transfer of axial thrust to the engine caused by jet pump failure.

[0001] This application relies for priority on U.S. Provisional PatentApplication Serial No. 60/371,726, filed on Apr. 12, 2002, entitled“Stator Vane and Impeller-Drive Shaft Arrangements and PersonalWatercraft Employing Same” The contents of that provisional patentapplication are incorporated herein by reference. This application is adivisional application of U.S. patent application Ser. No. 10/412,274,filed on Apr. 14, 2003, entitled “Stator Vane and Impeller-Drive ShaftArrangements and Personal Watercraft Employing the Same”, now pending.The content of that patent application are incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to jet powered watercraft, especiallypersonal watercraft (“PWC”). More specifically, the invention relates toa jet power assembly, in particular to an impeller and its associatedcomponents.

[0004] 2. Description of Related Art

[0005] Jet powered watercraft have become very popular in recent yearsfor recreational use and for use as transportation in coastalcommunities. The jet power offers high performance and allows thewatercraft to be more compact and fast. Accordingly, PWCs, whichtypically employ jet propulsion, have become common place, especially inresort areas.

[0006] A typical jet propulsion system for a PWC includes a jet pump.The jet pump pulls water in through an inlet, pressurizes it, and forcesit through a venturi resulting in a high pressure water jet. The resultis a reaction force called thrust that propels the PWC in the directionopposite to the water jet. Typically, a steering nozzle, located at thedischarge end of the pump, is controlled by a steering mechanism toredirect the water jet so as to effect steering of the PWC. The jet pumputilizes an impeller, rotated by an engine via a drive shaft (and/orimpeller shaft) to circulate and pressurize the water. However, thetypical impeller utilizes impeller blades that have a relatively largepitch. Accordingly, as the impeller is rotated, the water stream exitingthe impeller is directed into a relatively tight spiraling flow. Inorder to rectify or straighten the spiraling water stream, the typicaljet pump includes a non-rotating stator having blades to attenuate oreliminate the rotation of the flow.

[0007]FIG. 14 shows a conventional jet pump, which can be used in ajet-propelled watercraft, indicated at 800. The jet pump 800 includes arigid housing 802 within which a stator 804 is fixedly mounted. Animpeller 806 is rotatably mounted to the stator.804 via an impellershaft 808. As shown, the impeller 806 includes a plurality of impellerblades 810. The stator 804 includes a plurality of stator vanes 812. Apump cover 814 is fastened to a rearward end of the stator 804 with,e.g., fasteners 816. A venturi 818 is connected to the housing 802rearward of the stator 804. The connecting element 808 is fixedlyconnected to the impeller 806 and rotates with the impeller 806 relativeto the stator 804 on bearings 820. The bearings 820 are disposed withina cavity 822 within the stator 804, which is typically filled with alubricant. A seal 824 prevents debris and water from entering the cavity822. The pump cover 814 protects the impeller shaft 808 and bearings 820and encloses the cavity 822 to prevent lubricant leakage. The pump cover814 is conically configured to facilitate the flow of water through theventuri 818. The venturi 818 sometimes includes a plurality of fins 826therein that extend radially inwardly therefrom.

[0008] In operation, an engine is coupled to the impeller 806 via adrive shaft (not show) to thereby rotate the impeller 806. The impeller806 thus pulls water from the body of water and pressurizes the water asthe impeller 806 is rotated. Due to the rotational speed of the impeller806 and to the pitch of the blades 810, water being pressurized by theimpeller 806 assumes a spiraling flow as it exits the impeller 806. Thestator varies 812 extend relatively co-extensively to the axialdirection of the jet pump 800 and serve to straighten or rectify thespiraling flow of water as it passes therethrough. The flow of water isaccelerated in a progressive manner as the flow travels axially past theimpeller 806 due to the progressive increase in diameter of the impellerhub 811. The flow of water exits the stator 804 and enters the venturi818. A gradual reduction in diameter of the venturi 818 serves toconverge the flow of water and also accelerates the flow. The venturi818 includes an outlet opening 828 through which the flow of water exitsthe jet pump 800 to propel the watercraft.

[0009]FIG. 15 shows the stator 804 in relatively greater detail. Asshown, each of the stator vanes 812 is curved to facilitaterectification of the flow of water from the impeller 806. Additionally,each of the vanes 812 has a cross-sectional configuration similar tothat of an airfoil with a trailing edge that is slightly tapered. Theairfoil-like configuration serves to facilitate flow of water past thestator vanes 812. However, the stator vanes 812 have a relativelyconstant thickness, typically about 2-5 mm. Since the stator vanes 812are angled at their leading edge and progressively straighten out towardtheir trailing edge, and a flow area between the blades at the trailingedge portions is greater than a flow area between the blades at theleading edge portions, the flow of water decelerates as it moves pastthe vanes 812. The venturi 818 and pump cover 814 are tapered in theircross-sectional configurations so as to converge and pressurize thewater stream and, therefore, the water stream is accelerated as it flowspast. However, the deceleration of the water flow through the stator 804represents an energy loss that decreases the efficiency of the jet pump800.

[0010]FIG. 16 shows an improved type of jet pump 850, which is referredto as a converging type jet pump. As shown, the jet pump 850 has ahousing 852 that incorporates an integral venturi 854. The jet pump 850includes a stator 856 that has a plurality of stator vanes 858. A hub860 of the stator 856 has a conical configuration corresponding to thatof the venturi 854. The stator vanes 858 have an airfoil-likeconfiguration similar to those shown in FIG. 15, but may be arrangedwith a greater degree of curvature. Additionally, the stator vanes 858are also tapered (radially with respect to the stator hub 860) toconform to the venturi 854. Contrary to the stator 804 shown in FIG. 15,head loss through the stator 856 is reduced, since the cross-sectionalarea of the flow path between the stator vanes 858 is decreased due tothe tapered configuration of the venturi 854 along the length of thevanes 858, even though trailing edge portions of the vanes 858 arenarrower than the leading edge portions thereof. This design effectivelyeliminates the degrading head loss within the stator 856. However,typical manufacturing processes for producing stators, i.e., casting,may not be used or is highly costly due to the conical shape of the hub860 and configuration of the vanes 858. Therefore, other more costly andinefficient methods of manufacture must be used to create the stator856.

[0011] For at least these reasons, a need has developed for a jet pumpthat is highly efficient and is easily manufactured.

[0012] Another consideration with operation of PWCs is the creation ofnoise pollution during the operation thereof. The use of internalcombustion engines operating at high RPMs make conventional watercrafttypically quite noisy to operate. Technological advances in-engine noiseattenuation systems have dramatically decreased the operating volume ofthe engine in typical PWCs. Accordingly, now, noise from the jet pump ofthe jet propulsion system is a greater concern. In particular, animpeller of the jet pump is rotated at a relatively high RPM to generatesufficient power for the PWC. The interaction of the spatiallynon-uniform velocity distribution at the impeller discharge with thestator vanes of the stator causes lift and drag fluctuations on thestator vanes and flow fluctuations within the stator vane passages. Inaddition, the periodic blockage of the flow in the impeller bladepassages by the stator vanes will result in similar force fluctuationson the impeller blades and also in flow pulsations within the bladepassages. Fluctuating forces may be transmitted directly through thefluid or through the vibrational response of the structure (liftfluctuations causing a net axial force component exciting the hub at thepump attachment location). Rotor-stator interaction noise is oftencalled “interaction tones” and can represent a relatively substantiallevel of noise. This is especially true when the relative rotationalspeed of the impeller and the stator reaches a critical frequency,wherein multiple fluctuating forces are simultaneously produced bymultiple impeller blades simultaneously passing respective stator vanes.

[0013] Conventional designs of stators, e.g., stator 804 shown in FIG.17, have oriented the stator vanes 812 at equal distances apart from oneanother, e.g., 10 vanes at 36° apart. Accordingly, as illustrated inFIG. 18, at a critical frequency (cf), based on the relative numbers andspeeds of the impeller blades and stator vanes, the volume level (dB) ofthe jet pump reaches a maximum (dB_(max)). There are also noise levelspikes (dBh1-dBh4) at the subsequent harmonic frequencies (cfh1-cfh4) ofthe critical frequency.

[0014] There is therefore a need in the art to provide a jet pump thatoperates at lower noise levels, or that at least reduces the criticalfrequencies, since the noise generated at these frequencies is moreirritating to the human ear.

[0015] Furthermore, another concern in operating a PWC is to preventengine failure due to pump failure. When ajet pump fails duringoperation of the PWC, the pump bearings often get damaged due to theloads and high rotational speed and can no longer take up the axialthrust generated by the impeller, which is then transferred to theengine via the drive shaft connected to the impeller. The transfer of asignificant axial load to the engine by the drive shaft is undesirable.

[0016] There is thus a need to prevent the transfer of the axial thrustcaused by jet pump failure to the engine.

SUMMARY OF THE INVENTION

[0017] One aspect of the invention is directed to a jet pump for awatercraft comprising a generally cylindrical housing, an impellerhaving a hub, a plurality of impeller blades mounted on the hub, and ashaft extending from the hub for connection to a rotatable drive shaft.The impeller is disposed within the housing so as to rotate within thehousing when driven by the rotatable drive shaft. A stator has aplurality of vane structures extending generally radially outwardlytherefrom and extending axially therealong. The impeller is rotationallyconnected to the stator to allow relative movement therebetween. Acoupling structure is coupled to the shaft, wherein the couplingstructure has an elongated configuration including a socket having amouth configured to receive the drive shaft and a bore disposed on anopposite side of the socket than the mouth so as to allow relative axialmovement between the impeller and the drive shaft.

[0018] In accordance with another aspect, the invention is directed to ajet pump for a watercraft comprising a generally cylindrical housinghaving a forward portion and a rearward portion thereof, an impellerhaving a plurality of impeller blades mounted thereon, the impellerbeing disposed within the forward portion of the housing and beingconfigured to be connected to a rotatable shaft so as to be rotatablewithin the housing, and a stator fixedly mounted within the housingadjacent to and rearward of the impeller. The stator has a plurality ofcircumferentially spaced first vane structures extending generallyradially outwardly therefrom, extending axially along the stator, andtapered in width axially toward the impeller. A pump cover is fixedlymounted to a rearward side of the stator and has a plurality ofcircumferentially spaced second vane structures extending generallyradially outwardly therefrom, extending axially along the pump cover,and tapered in width opposite the first vane structures. Each of theplurality of first vane structures abuts a respective one of theplurality of second vane structures. The pluralities of abutting firstand second vane structures define a plurality of stator vanes extendingaxially along the stator and the pump cover and being positionedrearward of said impeller.

[0019] In accordance with another aspect, the invention is directed to ajet pump for a watercraft comprising a generally cylindrical housinghaving a forward portion and a rearward portion thereof and an impellerhaving a plurality of impeller blades mounted thereon. The impeller isdisposed within the forward portion of the housing and is configured tobe connected to a rotatable shaft so as to be rotatable within thehousing. A stator is fixedly mounted within the housing adjacent to andrearward of the impeller. The impeller is configured to be rotationallycoupled to the stator to allow relative rotational movementtherebetween. The stator has a plurality of circumferentially spacedvanes extending generally radially outwardly therefrom and extendingaxially along the stator. Each of the vanes has a thickened intermediatesection disposed between a pair of opposed ends that taper from thethickened intermediate section.

[0020] A further aspect of the invention is directed to a stator for usein a jet pump having an impeller rotatably coupled with respect to thestator, comprising a central hub portion, and a plurality of statorvanes extending outward from the central hub portion arranged withirregular spacing between adjacent vanes. At least one stator vane isspaced from an adjacent stator vane a different distance than thatstator vane is spaced from its other adjacent stator vane.

[0021] An additional aspect of the invention is directed to an impellerfor use in ajet pump having a stator fixed with respect to the impeller,comprising a central hub portion connected to a drive assembly to rotatethe central hub portion, and a plurality of impeller blades extendingoutward from the central hub portion arranged with irregular spacingbetween adjacent blades. At least one impeller blade is spaced from anadjacent impeller blade a different distance than that impeller blade isspaced from its other adjacent impeller blade.

[0022] The jet pump in accordance with all of the embodiments of thepresent invention is preferably used in combination with a watercraft.

[0023] Preferably, the watercraft is a personal watercraft (PWC). ThePWC can be a straddle type seated PWC or a stand-up PWC. Additionally,the watercraft could be different types of jet powered watercraft, suchas ajet boat. The invention is directed to a jet pump, however, and isnot intended to be limited to a watercraft.

[0024] These and other aspects of this invention will become apparentupon reading the following disclosure in accordance with the Figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] An understanding of the various embodiments of the invention maybe gained by virtue of the following figures, of which like elements invarious figures will have common reference numbers, and wherein:

[0026]FIG. 1 illustrates a side view of a watercraft in accordance withpreferred embodiments of the invention;

[0027]FIG. 2 is a top view of the watercraft of FIG. 1;

[0028]FIG. 3 is a front view of the watercraft of FIG. 1;

[0029]FIG. 4 is a back view of the watercraft of FIG. 1;

[0030]FIG. 5 is a bottom view of the hull of the watercraft of FIG. 1;

[0031]FIG. 6 illustrates an alternative stand-up type watercraft;

[0032]FIG. 7 is a perspective view of a jet pump in partial crosssection having stator vanes in accordance with one preferred embodimentof the invention;

[0033]FIG. 8 is a side view in partial cross section of the jet pumpshown in FIG. 7;

[0034]FIG. 9 is a schematic view showing a series of stator vanes of thejet pump shown in FIG. 7 relative to the area of the housing;

[0035]FIG. 10 is a front view of a stator illustrating the non-uniformspacing of the stator vanes in accordance with another preferredembodiment of the invention;

[0036]FIG. 10A is a front schematic view of another stator in accordancewith the invention with non-uniform spacing between vanes;

[0037]FIG. 10B is a front schematic view of another stator in accordancewith the invention with non-uniform spacing between vanes;

[0038]FIG. 10C is a front schematic view an impeller in accordance withan embodiment of the invention showing non-uniform spacing betweenimpeller blades;

[0039]FIG. 11 is a graphical representation of noise levels generated bya jet pump having the stator shown in FIG. 10 relative to prior art jetpumps;

[0040]FIG. 12 is a partial cross-sectional view of a jet pump having acoupling structure between the impeller and drive shaft in accordancewith another preferred embodiment of the invention;

[0041]FIG. 13 is an enlarged partial cross-sectional view of a couplingstructure between two interconnected drive shafts in accordance withanother embodiment of the present invention;

[0042]FIG. 14 is a side view in cross section of a prior art jet pump;

[0043]FIG. 15 is a partial perspective view of an impeller of the jetpump shown in FIG. 14;

[0044]FIG. 16 is a side view in partial cross section of another priorart jet pump;

[0045]FIG. 17 is a front schematic view of a prior art stator; and

[0046]FIG. 18 is a graphical representation of noise levels generated bya prior art jet pump having the stator of FIG. 17.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0047] The invention is described with reference to a PWC for purposesof illustration only. However, it is to be understood that the jetpropulsion assembly described herein can be utilized in any watercraft,such as sport boats. Moreover, the watercraft details described hereinare not intended to limit the invention, but rather to providebackground for one possible implementation of the invention.

[0048] The general construction of a personal watercraft 10 inaccordance with a preferred embodiment of this invention is shown inFIGS. 1-5. The following description relates to one way of constructinga personal watercraft according to a preferred design. Obviously, thoseof ordinary skill in the watercraft art will recognize that there areother known ways of manufacturing and designing watercraft and that thisinvention would encompass other known ways and designs.

[0049] The watercraft 10 of FIG. 1 is made of two main parts, includinga hull 12 and a deck 14. The hull 12 buoyantly supports the watercraft10 in the water. The deck 14 is designed to accommodate a rider and, insome watercraft, one or more passengers. The hull 12 and deck 14 arejoined together at a seam 16 that joins the parts in a sealingrelationship. Preferably, the seam 16 comprises a bond line formed by anadhesive. Of course, other known joining methods could be used tosealingly engage the parts together, including but not limited tothermal fusion, molding or fasteners such as rivets or screws. A bumper18 generally covers the seam 16, which helps to prevent damage to theouter surface of the watercraft 10 when the watercraft 10 is docked, forexample. The bumper 18 can extend around the bow, as shown, or aroundany portion or all of the seam 16.

[0050] The space between the hull 12 and the deck 14 forms a volumecommonly referred to as the engine compartment 20 (shown in phantom).Shown schematically in FIG. 1, the engine compartment 20 accommodates anengine 22, as well as a muffler, tuning pipe, gas tank, electricalsystem (battery, electronic control unit, etc.), air box, storage bins24, 26, and other elements required or desirable in the watercraft 10.One of the challenges of designing the watercraft 10 is to fit all ofthese elements into the relatively small volume of the enginecompartment 20.

[0051] As seen in FIGS. 1 and 2, the deck 14 has a centrally positionedstraddle-type seat 28 positioned on top of a pedestal 30 to accommodatea rider in a straddling position. The seat 28 may be sized toaccommodate a single rider or sized for multiple riders. For example, asseen in FIG. 2, the seat 28 includes a first, front seat portion 32 anda rear, raised seat portion 34 that accommodates a passenger. The seat28 is preferably made as a cushioned or padded unit or interfittingunits. The first and second seat portions 32, 34 are preferablyremovably attached to the pedestal 30 by a hook and tongue assembly (notshown) at the front of each seat and by a latch assembly (not shown) atthe rear of each seat, or by any other known attachment mechanism. Theseat portions 32, 34 can be individually tilted or removed completely.One of the seat portions 32, 34 covers an engine access opening (in thiscase above engine 22) defined by a top portion of the pedestal 30 toprovide access to the engine 22 (FIG. 1). The other seat portion (inthis case portion 34) can cover a removable storage box 26 (FIG. 1). A“glove compartment” or small storage box 36 may also be provided infront of the seat 28.

[0052] As seen in FIG. 4, a grab handle 38 may be provided between thepedestal 30 and the rear of the seat 28 to provide a handle onto which apassenger may hold. This arrangement is particularly convenient for apassenger seated facing backwards for spotting a water skier, forexample. Beneath the handle 38, a tow hook 40 is mounted on the pedestal30. The tow hook 40 can be used for towing a skier or floatation device,such as an inflatable water toy.

[0053] As best seen in FIGS. 2 and 4 the watercraft 10 has a pair ofgenerally upwardly extending walls located on either side of thewatercraft 10 known as gunwales or gunnels 42. The gunnels 42 help toprevent the entry of water in the footrests 46, provide lateral supportfor the rider's feet, and also provide buoyancy when turning thewatercraft 10, since personal watercraft roll slightly when turning.Towards the rear of the watercraft 10, the gunnels 42 extend inwardly toact as heel rests 44. Heel rests 44 allow a passenger riding thewatercraft 10 facing towards the rear, to spot a water-skier forexample, to place his or her heels on the heel rests 44, therebyproviding a more stable riding position. Heel rests 44 could also beformed separate from the gunnels 42.

[0054] Located on both sides of the watercraft 10, between the pedestal30 and the gunnels 42 are the footrests 46. The footrests 46 aredesigned to accommodate a rider's feet in various riding positions. Tothis effect, the footrests 46 each have a forward portion 48 angled suchthat the front portion of the forward portion 48 (toward the bow of thewatercraft 10) is higher, relative to a horizontal reference point, thanthe rear portion of the forward portion 48. The remaining portions ofthe footrests 46 are generally horizontal. Of course, any contourconducive to a comfortable rest for the rider could be used. Thefootrests 46 may be covered by carpeting 50 made of a rubber-typematerial, for example, to provide additional comfort and traction forthe feet of the rider.

[0055] A reboarding platform 52 is provided at the rear of thewatercraft 10 on the deck 14 to allow the rider or a passenger to easilyreboard the watercraft 10 from the water. Carpeting or some othersuitable covering may cover the reboarding platform 52. A retractableladder (not shown) may be affixed to the transom 54 to facilitateboarding the watercraft 10 from the water onto the reboarding platform52.

[0056] Referring to the bow 56 of the watercraft 10, as seen in FIGS. 2and 3, watercraft 10 is provided with a hood 58 located forwardly of theseat 28 and a helm assembly 60. A hinge (not shown) is attached betweena forward portion of the hood 58 and the deck 14 to allow hood 58 tomove to an open position to provide access to the front storage bin 24(FIG. 1). A latch (not shown) located at a rearward portion of hood 58locks hood 58 into a closed position. When in the closed position, hood58 prevents water from entering front storage bin 24. Rearview mirrors62 are positioned on either side of hood 58 to allow the rider to seebehind. A hook 64 is located at the bow 56 of the watercraft 10. Thehook 64 is used to attach the watercraft 10 to a dock when thewatercraft is not in use or to attach to a winch when loading thewatercraft on a trailer, for instance.

[0057] As best seen in FIGS. 3, 4, and 5, the hull 12 is provided with acombination of strakes 66 and chines 68. A strake 66 is a protrudingportion of the hull 12. A chine 68 is the vertex formed where twosurfaces of the hull 12 meet. The combination of strakes 66 and chines68 provide the watercraft 10 with its riding and handlingcharacteristics. Sponsons 70 are located on both sides of the hull 12near the transom 54. The sponsons 70 preferably have an arcuateundersurface that gives the watercraft 10 both lift while in motion andimproved turning characteristics. The sponsons are preferably fixed tothe surface of the hull 12 and can be attached to the hull by fastenersor molded therewith. Sometimes it may be desirable to adjust theposition of the sponson 70 with respect to the hull 12 to change thehandling characteristics of the watercraft 10 and accommodate differentriding conditions.

[0058] As best seen in FIGS. 1 and 2, the helm assembly 60 is positionedforwardly of the seat 28. The helm assembly 60 has a central helmportion 72, that may be padded, and a pair of steering handles 74, alsoreferred to as a handle bar. One of the steering handles 74 ispreferably provided with a throttle lever 76, which allows the rider tocontrol the speed of the watercraft 10. As seen in FIG. 2, a displayarea or cluster 78 is located forwardly of the helm assembly 60. Thedisplay cluster 78 can be of any conventional display type, includingdials or LED (light emitting diodes). The central helm portion 72 mayalso have various buttons 80, which could alternatively be in the formof levers or switches, that allow the rider to modify the display dataor mode (speed, engine rpm, time . . . ) on the display cluster 78 or tochange a condition of the watercraft 10 such as trim (the pitch of thewatercraft).

[0059] The helm assembly 60 may also be provided with a key receivingpost 82, preferably located near a center of the central helm portion72. The key receiving post 82 is adapted to receive a key (not shown)that starts the watercraft 10. As is known, the key is typicallyattached to a safety lanyard (not shown). It should be noted that thekey-receiving post 82 may be placed in any suitable location on thewatercraft 10.

[0060] Alternatively, this invention can be embodied in a stand-up typepersonal watercraft 120, as seen in FIG. 6. Stand-up watercraft 120 areoften used in racing competitions and are known for high performancecharacteristics. Typically, such stand-up watercraft 120 has a lowercenter of gravity and a more concave hull 122. The deck 124 may alsohave a lower profile. In this watercraft 120, the seat is replaced witha standing platform 126. The operator stands on the platform 126 betweenthe gunnels 128 to operate the watercraft. The steering assembly 130 isconfigured as a pivoting handle pole 132 that tilts up from a pivotpoint 134 during operation, as shown in FIG. 6. At rest, the handle pole132 folds downwardly against the deck 124 toward the standing platform126. Otherwise, the components and operation of the watercraft 120 aresimilar to watercraft 10.

[0061] Returning to FIGS. 1 and 5, the watercraft 10 is generallypropelled by a jet propulsion system that includes ajet pump 200,discussed in greater detail below. As known, the jet pump 200pressurizes water to create thrust. The water is first scooped fromunder the hull 12 through an inlet 86, which preferably has a grate (notshown in detail). The inlet grate prevents large rocks, weeds, and otherdebris from entering the jet propulsion system 200, which may damage thesystem or negatively affect performance. Water flows from the inlet 86through a water intake ramp 88. The top portion 90 of the water intakeramp 88 is preferably formed by the hull 12, and a ride shoe (not shownin detail) forms its bottom portion 92. Alternatively, the intake ramp88 may be a single piece or an insert to which the jet propulsion system84 attaches. In such cases, the intake ramp 88 and the jet pump 200 areattached as a unit in a recess in the bottom of hull 12.

[0062] From the intake ramp 88, water enters the jet pump 200. The jetpump 200 is located in a formation in the hull 12, referred to as thetunnel 94. The tunnel 94 is defined at the front, sides, and top by thehull 12 and is open at the transom 54. The bottom of the tunnel 94 isclosed by a ride plate 96. The ride plate 96 creates a surface on whichthe watercraft 10 rides or planes at high speeds.

[0063] As shown in FIG. 7, the jet pump 200 is made of two main parts:an impeller 202 and a stator 204. The impeller 202 is coupled to theengine 22 by one or more shafts 260, such as a driveshaft and/or animpeller shaft. The rotation of the impeller 202 pressurizes the water,which then moves over the stator 204 and the pump cover 216, both ofwhich define a plurality of stator vanes 220. The role of the statorvanes 220 is to decrease the rotational motion of the water so thatalmost all the energy given to the water is used for thrust, as opposedto swirling the water. Once the water leaves the jet propulsion system200, it goes through a venturi 230. Since the venturi's exit diameter issmaller than its entrance diameter, the water is accelerated further,thereby providing more thrust. Referring back to FIGS. 1-6, a steeringnozzle 102 is pivotally attached to the venturi 230 so as to pivot abouta vertical axis 104. The steering nozzle 102 could also be supported atthe exit of the tunnel 94 in other ways without a direct connection tothe venturi 100.

[0064]FIGS. 7 and 8 show one contemplated embodiment of a jet pump 200embodying principles of the present invention. The jet pump 200 includesa rotatable impeller 202 and a non-rotatirig stator 204. The impeller202 and stator 204 are housed within a generally cylindrical housing206. The housing 206 defines an axial direction of the jet pump 200along line A. The impeller 202 is rotatably coupled to the stator body214 via a connecting element and bearings (not shown). It iscontemplated that the impeller 202 may be rotatably coupled to thestator 204 with a conventional connecting arrangement, such as thatshown in FIG. 14. Of course, any other suitable arrangement may be used.

[0065] The impeller 202 includes a plurality of impeller blades 208extending generally radially outwardly from and circumferentially aboutan impeller hub 210. The stator 204 includes a plurality of first statorvane portions 212 extending generally radially outwardly from andgenerally axially along a stator body 214. The stator body 214 is heldrelatively stationary relative to the housing 206 by the stator vanes212 extending therebetween and coupled to the housing 206. A pump cover216 is mounted to the stator body 214 opposite the impeller 202 in anyconventional manner, such as with threaded fasteners (not shown). Thepump cover 216 includes a plurality of second stator vane portions 218extending radially outwardly therefrom and generally axially therealong.The first stator vane portions 212 and second stator vane portions 218abut and cooperate with one another when the pump cover 216 is mountedto the stator body 214 to define a plurality of stator vanes 220. Thepump cover 216 includes a generally conical pump cover body 222.

[0066] As shown, the housing 206 defines an inlet 224 at an axiallyforward end thereof and an outlet 226 at an axially rearward endthereof. The housing 206 includes a main body portion 228 within aninterior of which is disposed the impeller 202 and at least a portion ofthe stator 204. The main body portion 228 has a relatively constantcross-sectional configuration and area along an axial extent thereof.Rearward of the main body portion 228, the housing 206 defines a taperedventuri portion 230. The pump cover 216, preferably with a portion ofthe stator vanes 220, is disposed within the venturi portion 230. Asshown, the venturi portion 230 has a decreasing or taperedcross-sectional configuration and area along an axial extent thereof.The housing 206 can be formed as a single piece or a plurality of piecessecured together, either removably or permanently, as by welding.

[0067] As shown in FIG. 8, a cross-sectional configuration and areadefined by an interior of the housing 206 is relatively constant alongthe axial extent of the main body portion 228. The cross-sectionalconfiguration and area of the interior of the housing 206, however,decreases along the axial extent of the venturi portion 230. However, anactual or effective cross-sectional area within which water may flow(i.e., flow area) through the jet pump 200 generally decreases along anentire axial extent of thereof. This is effected due to an increase indiameter of the impeller hub 210, which is conically or hemisphericallyshaped, an increase in volume of the first stator vane portions 212, andthe respective tapered diameters of the pump cover 216 and venturiportion 230. A continuous decrease in flow area of the jet pump 200ensures that a flow of water therein continuously accelerates throughoutthe axial extent of the jet pump 200, thereby maximizing efficiency ofthe pump 200.

[0068] As shown in FIG. 9, leading edge portions 232 of the first statorvane portions 212 are relatively narrower than trailing edge portions234 thereof. The terms leading and trailing herein refer to thedirection of water flow wherein the leading edge is the upstream edgeand the trailing edge is the downstream edge. Additionally, an interiordiameter of the housing 206 at the leading edge portions 232, indicatedby circle 236, is relatively equivalent to an interior diameter of thehousing 206 corresponding to the trailing edge portion 234, which isindicated at circle 238. Accordingly, a flow area corresponding to theselocations progressively decreases along the axial extent of the firstvane portions 212, due to the increasing width of the vane portions 212.

[0069] Conversely, leading edge portions 240 of the second stator vaneportions 218 are relatively wider than trailing edge portions 242thereof. However, as denoted by circle 244, an internal diameter of thehousing 206 gradually decreases along the axial extent of the taperedventuri portion 230. Therefore, even though the area of the secondstator vane portions 218 decreases along the axial extent thereof, theoverall flow area continues to decrease due to the decrease in theinternal diameter of the housing 206. This arrangement ensurescontinuous acceleration of water flow through the pump 200.

[0070] The first stator vane portions 212 and the second stator vaneportions 218 connect to form relatively wide stator vanes 220 that havean arcuate airfoil shape, as clearly seen in FIG. 9. Preferably, thestator vanes 220 made of first stator vane portion 212 and second statorvane portion 218 have a thickness of about 2 mm at their outer ends anda central thickness of about 15 mm. This thickness is considerablygreater than conventional prior art stator vanes, which typically have aconstant thickness of about 2-5 mm. The arrangement of the stator 204and pump cover 216 may be particularly advantageous, since, combinedwith the housing 206 having the integral venturi portion 230, water flowis continuously accelerated through the pump 200. Additionally, thestator 204 and pump cover 216 may be relatively easily andcost-effectively manufactured, such as by casting. In particular, sincethe stator body 214 is generally cylindrical and the vane portions 212increase in width in the rearward direction, the stator 204 may be castin a relatively simple and cost-effective manner. Likewise, since boththe pump cover body 222 and the second stator vane portions 218 taper inthe rearward direction, the pump cover 216 may be cast in a relativelysimple manner. The pump cover 216 may then be connected to a rearwardend of the stator 204 with, e.g., fasteners, thereby abutting the firstand second stator vane portions 212, 218 to define the plurality ofstator vanes 220. Furthermore, an effective length of the stator vanes220 may be increased relative to prior art designs while maintainingease of manufacture. Moreover, the venturi portion 230 of the housing206 need not include additional fins or vanes as do the conventionaltypes of jet pumps, which typically do not have pump covers with statorvanes thereon.

[0071] Another alternative for the stator vane 220 construction is tomake one piece, thickened vanes. This could be accomplished with acomplex mold for example. In that case, the vanes could be supported bythe stator or by the pump cover.

[0072] Referring back to FIG. 8, as the impeller 202 is rotated, each ofthe blades 208 produces a pressure wave, shown schematically at 250,which consecutively contacts leading edges of the stator vanes 220 in adirection corresponding to a direction of rotation of the impeller 202.At each contact between the pressure wave 250 and the spaced statorvanes 220, a pulse is generated. The frequency of these pulses is basedupon the numbers of impeller blades 208 and stator vanes 220, as well asthe relative spacings thereof. The level of noise generated by the pump200 depends on the frequency and amplitude of the pulses.

[0073] In prior art pump designs, as discussed previously, large noiselevels are generated at a critical frequency, due to the rotor-statorinteraction. As shown by the graphical representation of the noise levelin FIG. 11, the solid line represents a prior art jet pump that producesa significantly large noise level (dB_(max)) when operated at thecritical frequency (cf) due to the constructive interference of thepulses. Subsequent harmonics (cfh1-cfh4) of the critical frequency alsogenerate a large noise level. Although shown as having a constantlydecreasing noise level in FIG. 11, it should be noted that this is onlyan example, dB_(max) could occur at any subsequent harmonics, and anyharmonics could have a higher or lower noise level than the precedingharmonics.

[0074]FIG. 10 shows a contemplated arrangement of stator blades 220according to another feature of the invention. As shown in thisarrangement, the stator blades 220 may be non-uniformly spaced about thestator body 214 and pump cover 216. For example, spacing between a pairof stator vanes 220A, 220B (shown as 37°) is different than spacingbetween an adjacent pair of vanes 220A, 220C (shown as 43°).Additionally, the vanes 220 may be arranged such that diametricallyopposed vanes do not align with one another. More particularly, thestator vanes 220 are preferably spaced such that at least one trailingedge of the plurality of impeller blades 208 is circumferentially offsetfrom the leading edge of any of the stator vanes 220 for any relativerotational position of the impeller 202 and stator 204. A substantialnoise reduction may be obtained with an arrangement of stator vanes 220in which only one trailing edge of the total number of impeller blades208 is circumferentially offset from the stator vanes 220. However, itmay be preferable for the arrangement of stator vanes 220 to allow foronly one trailing edge of the impeller blades 208 to align with theleading edge of a stator vane 220 for any relative rotational positionof the impeller 202 and stator 204. For example, a noise reduction maybe obtained with a three-bladed impeller by arranging the stator vanes220 such that only two trailing edges of the impeller blades may alignwith the leading edges of stator vanes 220 at any one time. However, agreater noise reduction may be obtained if the stator vanes 220 arearranged such that only one trailing edge of the impeller blades mayalign with a leading edge of the stator vanes 220 at any one time. Theactual arrangement of the stator vanes 220 will depend on which criticalfrequency/frequencies need to be addressed.

[0075] A similar result can be achieved by redesigning a conventionalstator having evenly spaced stator vanes, such as stator 804 of FIG. 17,and removing one or more stator vanes. FIG. 10A shows a stator 300 withstator vanes 302 that are spaced unevenly apart, with effectively onevane removed. As seen, stator vane 302A and stator vane 302B, forexample, are spaced approximately 36° apart, while stator vane 302A andstator vane 302C are spaced approximately 72° apart. FIG. 10B shows asimilar stator 310 with four vanes 312 effectively missing. In thiscase, stator vanes 312A and 312B are approximately 72° apart, statorvanes 312B, 312C and 312D are approximately 36° apart, and stator vanes312D and 312E are approximately 108° apart, as seen. Of course otherarrangements and configurations can be employed while still remainingwithin the scope of this concept.

[0076]FIG. 10C shows another variation of the concept of uneven spacingin which the impeller. 320 has unevenly spaced impeller blades 322. Asseen, the edge of impeller blade 322A is offset from the edge ofimpeller blade 322B by approximately 162°, the edge of impeller blade322B is offset from the edge of impeller blade 322C by approximately90°, and the edge of impeller blade 322C is offset from the edge ofimpeller blade 322A by approximately 108°. The uneven spacing of theimpeller blades 322 achieves a similar effect as the unevenly spacedstator vanes by staggering pressure waves and subsequent pulses toeliminate interference.

[0077] As shown by the dotted line in the graph of FIG. 11, a statorhaving stator vanes that are unevenly spaced such that any number oftrailing edges of impeller blades less than the total number of impellerblades provided on the impeller passes over a stator vane at any onetime. Accordingly, the pressure waves and subsequent pulses arestaggered and, therefore, cannot constructively interfere with oneanother. This way, the noise level, especially at the critical frequencyand its harmonics, remains substantially lower than with prior artuniformly spaced vanes due to a lower amplitude of tones produced by theblade pass frequency and the more even amplitude distribution.

[0078] The unevenly spaced arrangement of stator vanes may beimplemented using the thick stator vanes 220 described above, or withconventional stator vanes, as shown in FIGS. 14-16.

[0079] In accordance with a third feature of the invention, FIG. 12shows a drive shaft or an impeller shaft 260 coupled to the impeller202. The drive shaft 260 may be connected directly to the engine 22 ormay be coupled to the engine 22 with one or more other shafts. Aconfronting end of the shaft 260 defines a splined connecting portion262 that engages within a splined socket 264 provided within a couplingstructure 266 of the impeller 202. While the coupling structure 266 isshown integrally formed with the impeller 202, it is contemplated thatthe coupling structure 266 may be separate and joined with the impeller202 with, e.g., fasteners, welding, etc. The coupling structure 266extends axially forwardly from the impeller hub 210 and provides thesocket 264 with a mouth in a forward end portion 268 thereof. Thecoupling structure 266 provides a splined connecting portion receivingspace or bore 270 therein between the socket 264 and the impeller hub210. An inner diameter of the bore 270 is relatively greater than thatof the socket 264. More specifically, the inner diameter of the bore 270is sufficiently large to allow the splined connecting portion 262 to bereceived therein. A sealing structure 272 may be provided between theshaft 260 and coupling structure 266 to prevent water and debris fromentering between the splined portion 262 and socket 264. Of course, theshaft 260 can be attached by any known method that permits rotation,such as a keyed coupling formation.

[0080] During operation, the torque transferred from the shaft 260 tothe impeller 202 creates an axial thrust component that is transferredto the pump bearings, such as bearings 274. In the event of a failure ofthe bearings, if the axial thrust is sufficiently large, the couplingstructure 266 moves axially relative to the shaft 260 such that anentire axial extent of the splined portion 262 can be received withinthe bore 270, which has an axial extent at least equal to that of thesplined portion 262. Once the splined portion 262 is entirely receivedwithin the bore 270, splined engagement between the splined portion 262and socket 264 is released, thereby allowing relative rotationalmovement between the shaft 260 and impeller 202, and eliminating thetransfer of torque from the shaft 260 to the impeller 202. Since no moretorque is transferred to the impeller, the axial thrust component isalso eliminated. This prevents the undesirable transfer of axial thrustto the engine. Furthermore, the axial extent of the bore 270 should besufficient to allow for a maximum axial displacement of the impeller 202during failure of the jet pump 200. Accordingly, the impeller 202 doesnot transfer the axial thrust to the engine via the shaft 260 whenfailure occurs. This spacing feature differs from conventional prior artdesigns, such as shown in FIG. 14, in which the splined correction isdisposed directly adjacent to the impeller hub.

[0081] It is contemplated that the coupling structure 266, rather thanbeing connected to the impeller 202, may be connected between the engineand the output shaft thereof to effect the same function as describedabove. Any known coupling structure could be used, especially thoseknown to accommodate rotational movement.

[0082] It is also contemplated that a similar concept may be applied toa coupling structure, such as that shown at 280 in FIG. 13, betweenmultiple drive shafts of a PWC connecting the engine and jet pump. Asshown, a pair of shafts 282, 284 is provided, one having the couplingstructure 280 on a confronting end thereof. It is contemplated that thecoupling structure 280 may be integrally formed with one of the shafts282, 284 or may be separate and connected thereto with, e.g., fasteners,welding, etc. The coupling 280 includes a splined socket 286, with amouth that receives a splined end portion 288 of the opposite shafttherein. The coupling 280 also includes a splined end portion receivingspace or bore 290 between the socket 286 and shaft 282. A seal structure292 may be provided to prevent water and debris from entering the socket286. As described previously, when an axial thrust imparted by pumpfailure axially moves one of the shafts relative to the other, thesplined end portion 288 is received within the bore 290. Sufficientaxial displacement of the shafts 282, 284 will disengage the splined endportion 288 from the socket 286 to allow relative rotation therebetween,thereby eliminating the transfer of torque between shafts 282, 284, andtherefore the axial thrust. This prevents the undesirable transfer ofaxial thrust to the engine.

[0083] The coupling structures 266, 280, described herein, can be usedin combination with the impeller assembly described above or with anytype of conventional impeller construction. It would even be possible toemploy such a spaced coupling structure in a propeller driven system,particularly between the propeller and the drive shaft.

[0084] Although the above description contains specific examples of thepresent invention, these should not be construed as limiting the scopeof the invention but as merely providing illustrations of some of thepresently preferred embodiments of this invention. Thus, the scope ofthe invention should be determined by the appended claims and theirlegal equivalents rather than by the examples given.

[0085] Additionally, as noted previously, this invention is not limitedto PWC. For example, the stator vane and impeller-drive shaftarrangements disclosed herein may also be useful in jet powered outboardengines, sport boats or other floatation devices other than thosedefined as personal watercrafts, or any impeller driven device.

What is claimed is:
 1. A stator for use in a jet pump having an impellerrotatably coupled with respect to the stator, comprising: a central hubportion; and a plurality of stator vanes extending outward from thecentral hub portion arranged with irregular spacing between adjacentvanes, such that at least one stator vane is spaced from an adjacentstator vane a different distance than that stator vane is spaced fromits other adjacent stator vane.
 2. A watercraft comprising: a) a hull;b) an engine supported by the hull; and c) a jet pump supported by thehull, the jet pump including an impeller, and the stator of claim
 1. 3.An impeller for use in a jet pump having a stator fixed with respect tothe impeller, comprising: a) a central hub portion operativelyconnectable to an engine to rotate the central hub portion; and b) aplurality of impeller blades extending outward from the central hubportion arranged with irregular spacing between adjacent blades, suchthat at least one impeller blade is spaced from an adjacent impellerblade a different distance than that impeller blade is spaced its otheradjacent impeller blade.
 4. A watercraft comprising: a) a hull; b) anengine supported by the hull; and c) a jet pump supported by the hull,the jet pump including a stator, and the impeller of claim 3, whereinthe central hub portion is operatively connected to the engine.
 5. A jetpump comprising: a) an impeller having: a central hub; a plurality ofimpeller blades extending outward from the central hub portion arrangedwith irregular spacing between adjacent blades, such that at least oneimpeller blade is spaced from an adjacent impeller blade a differentdistance than that impeller blade is spaced its other adjacent impellerblade; b) a stator, fixed with respect to the impeller, having: acentral hub portion; and a plurality of impeller blades extendingoutward from the central hub portion arranged with irregular spacingbetween adjacent blades, such that at least one impeller blade is spacedfrom an adjacent impeller blade a different distance than that impellerblade is spaced its other adjacent impeller blade.
 6. A watercraftcomprising: a) a hull; b) an engine supported by the hull; c) the jetpump of claim 5, wherein the central hub portion of the impeller isoperatively connected to the engine.